FLT1 and cancer: FLT1/VEGFR1 is part of the HIF1–VEGF signaling pathway, playing an essential role in the development of embryonic vasculature in limiting the excessive proliferation of embryonic endothelial cells, and in adult PGF-mediated endothelial proliferation, the regulation of angiogenesis, cell survival, cell migration, macrophage function, chemotaxis, and cancer cell invasion.